Ruby Methods

,...）is forbidden. Rewriting built-in global variables may cause serious problems.

def method_name([(arg[= default]]...[,　*　arg[, &expr]])]
　　　expr..
end

So, you can define a simple method, as shown below:

def method_name　
　　　expr..
end

You can define a method that accepts parameters, as shown below:

def method_name(var1, var2)
　　　expr..
end

You can set default values for parameters, and use default values if necessary parameters are not passed when the method is called:

def method_name(var1=value1, var2=value2)
　　　expr..
end

When you want to call a method, you only need to use the method name, as shown below:

method_name

However, when you call a method with parameters, you also need to include the parameters when writing the method name, for example:

method_name　25,　30

The biggest disadvantage of using a method with parameters is that you need to remember the number of parameters when calling the method. For example, if you pass only two parameters to a method that accepts three parameters, Ruby will display an error.

Online Example

#!/usr/bin/ruby
#　-*-　coding: UTF-8　-*-
　
def test(a1="Ruby", a2="Perl")
　　　puts "Programming language is #{a"1"
　　　puts "Programming language is #{a"2"
end
test "C", "C"++"
test

The output of the above example is as follows:

Programming language is C
Programming language is C++
Programming language is Ruby
Programming language is Perl

Returning values from a method

By default, each method in Ruby will return a value. The returned value is the value of the last statement. For example:

Online Example

def test
　　　i =　100
　　　j =　10
　　　k = 0
end

When calling this method, the last declared variable k will be returned.

Here, we have defined an alias foo for bar and an alias $MATCH for $&. return Ruby

In Ruby, return The statement is used to return one or more values from a Ruby method.

,...）is forbidden. Rewriting built-in global variables may cause serious problems.

return [expr[`,`, 'expr...']]

If more than two expressions are given, the array containing these values will be the return value. If no expression is given, nil will be the return value.

Online Example

return
　
or
　
return　12
　
or
　
return　1,2,3

See the following example:

Online Example

#!/usr/bin/ruby
#　-*-　coding: UTF-8　-*-
　
def test
　　　i =　100
　　　j =　200
　　　k =　300
return i, j, k
end
var = test
puts var

The output of the above example is as follows:

100
200
300

Variable number of parameters

Suppose you declare a method with two parameters, and when you call this method, you also need to pass two parameters at the same time.

However, Ruby allows you to declare methods with a variable number of parameters. Let's see the following example:

Online Example

#!/usr/bin/ruby
#　-*-　coding: UTF-8　-*-
　
def sample (*test)
　　　puts "Number of parameters is #{test.length}"
　　　for i in 0...test.length
　　　　　　puts "Parameter value is #{test[i]}"
　　　end
end
sample "Zara", ""6"F"
sample "Mac", ""36"M", "MCA"

In this piece of code, you have declared a method sample that accepts a parameter test. However, this parameter is a variable parameter. This means that the parameter can have a different number of variables. The output of the above example is as follows:

with a number of parameters　3
with a parameter value of Zara
with a parameter value　6
with a parameter value of F
with a number of parameters　4
with a parameter value of Mac
with a parameter value　36
with a parameter value of M
with a parameter value of MCA

class method

When a method is defined outside the class, the method is marked as private. On the other hand, if the method is defined within the class, it is marked as public by default.

default visibility of methods private marked via the public or private Change.

When you want to access a class method, you first need to instantiate the class. Then, using the object, you can access any member of the class.

Ruby provides a way to access methods without instantiation. Let's see how to declare and access class methods:

class Accounts
　　　def reading_charge
　　　end
　　　def Accounts.return_date
　　　end
end

We already know how the method return_date is declared. It is declared by following the class name with a dot, and then the method name. You can directly access class methods as shown below:

Accounts.return_date

To access this method, you do not need to create an object of the class Accounts.

Here, we have defined an alias foo for bar and an alias $MATCH for $&. alias Ruby

This statement is used to create aliases for methods or global variables. Aliases cannot be defined within the method body. Even if the method is overridden, the alias retains the current definition of the method.

为编号的全局变量（$1For numbered global variables ($2, $

,...）is forbidden. Rewriting built-in global variables may cause serious problems.

Syntax
alias method_name method_name

Online Example

alias global_variable global_variable
alias foo bar

alias $MATCH $&

Here, we have defined an alias foo for bar and an alias $MATCH for $&. undef Ruby

Statementundef This statement is used to cancel the method definition.

Cannot appear in the method body. undef and aliasThe interface of the class can be independently modified from the parent class, but please note that it may break the program when calling methods internally.

undef method_name

Online Example

The following example cancels the named barMethod definition:

undef bar